The prevalence of hypertension and hypertension control among married Namibian couples

Background Previous studies suggest that having a marital partner with hypertension is associated with an individual’s increased risk of hypertension, however this has not been investigated in sub-Saharan Africa despite hypertension being a common condition; the age-standardised prevalence of hypertension was 46.0% in 2013 in Namibia. Objective To explore whether there is spousal concordance for hypertension and hypertension control in Namibia. Methods Couples data from the 2013 Namibia Demographic and Health Survey were analysed. Bivariable and multivariable logistic regression models were used to explore the odds of individual’s hypertension based on their partner’s hypertension status, 492 couples. and the odds of hypertension control in individuals based on their partner’s hypertension control (121 couples), where both members had hypertension. Separate models were built for female and male outcomes for both research questions to allow independent consideration of risk factors to be analysed for female and males. Results The unadjusted odds ratio of 1.57 (CI 1.10–2.24) for hypertension among individuals (both sexes) whose partner had hypertension compared to those whose partner did not have hypertension, was attenuated to aOR 1.35 (CI 0.91–2.00) for females (after adjustment for age, BMI, diabetes, residence, individual and partner education) and aOR 1.42 (CI 0.98–2.07) for males (after adjustment for age and BMI). Females and males were significantly more likely to be in control of their hypertension if their partner also had controlled hypertension, aOR 3.69 (CI 1.23–11.12) and aOR 3.00 (CI 1.07–8.36) respectively. Conclusions Having a partner with hypertension was positively associated with having hypertension among married Namibian adults, although not statistically significant after adjustment. Partner’s hypertension control was significantly associated with individual hypertension control. Couples—focused interventions, such as routine partner screening of hypertensive individuals, could be developed in Namibia.

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Authors' response: Our authorisation to download and use the Namibian Survey data from the DHS Program was granted on the 29th April 2020. Reference number:142031.

Our updated Data Availability statement…
This was a retrospective study using third party data from the 2013 Namibian Demographic and Health Survey. DHS data are publicly available through the (https://dhsprogram.com/methodology/survey/survey-display-363.cfm ).
4. Please include your full ethics statement in the 'Methods' section of your manuscript file. In your statement, please include the full name of the IRB or ethics committee who approved or waived your study, as well as whether or not you obtained informed written or verbal consent. If consent was waived for your study, please include this information in your statement as well.

Authors' response: Our ethics statement is now included within the Methods, on page 4.
'The 2013 Namibian DHS questionnaires and procedures were reviewed and approved by the ICF Institutional Review Board and the Ministry of Health and Social Services Biomedical Research Committee. All participants gave written consent prior to taking part in the DHS questionnaires and having their blood pressure measured.(14) All data were fully anonymized by the DHS program before we accessed them for our study. (14) Ethics approval for our study was granted by the University of Southampton Ethics and Research Governance Online (ERGO) committee.' Additional Editor Comments: The reviewers have raised important concerns on your submission that need to be addressed. The following points were emphasized: weak data interpretation and that conclusions are not based on data; editorial and citation related issues; clarity on variable measurement and operational definition; survey weight; lack of adequate description about the study setting and population including inclusion and exclusion criteria; data quality; and the need for a substantial improvement of the discussion as it has been a shallow presentation. The authors should provide a point-by-point response to these and other comments of the reviewers in their revised submission.
Authors' response: Thank you for the additional editor comments, we have set out to address each of these concerns within our revised manuscript.

Review Comments to the Author
Reviewer #1: Weare et al. presented the study to explore the spousal concordance for hypertension (HP) and hypertension control in Namibia. The data from Namibia Demographic and Health Survey were analysed to investigate the relationship between spouse, HP as well as disease control. They identified that, in Namibian adults, the partnership is correlated with HP and its control. The method is straightforward and the figures are easy to follow. This paper addressed a significant clinical problem, and the results are original with novelty in the target population. My major concern in this study is that the data interpretation is weak and the conclusion could not be fully supported based on the current context.

Authors' response:
We are really pleased that you felt our focus on couples has novelty and that our paper investigates a significant clinical problem. Thank you for all your comments, we believe changes made in response to your comments have strengthened our paper.
1. In methods for the built variable models: although bivariable models and multivariable models have been widely used, the models are more than what is included in the methods. Please explain the rationale for using each model (especially for the multivariable model), and provide citations of similar studies using the same model before.

Authors' response:
We have now included citations to past hypertension concordance studies that we used when deciding on the data analysis for our study (page 6). We have also expanded on the rationale for the models used.
2. In lines 182-183 "with the exception of partner age": from Table 1 partner characteristics, BMI status also showed a difference here, while authors did not cover the exception. Please clarify.

Authors' response:
We have edited the text to also include partner BMI status as this was another exception (Page 11 -'In general, male hypertension prevalence differed significantly across levels of all the female partner characteristics considered, while female hypertension prevalence remained similar across levels of the male partner characteristics except for partner age (p= 0.04) and partner BMI (p=0.05).') 3. In lines 183-184: the authors argued the HP prevalence in partner status, while no data was presented in the table. Please explain how these prevalence data are generated.
Authors' response: Thank you for your comment. We have edited the text and now refer to the data presented in the table.
Authors' response: This text has been moved to 'Spousal concordance in hypertension control' page 16 and refers to percentages within Table 4.

Please explain what is the gray box in the final columns of the tables.
Authors' response: The grey boxes were used to blank out empty boxes for variables not included in the final multivariable model, these grey boxes have been removed to make the tables clearer.
6. In Table 4, The Pearson test showed the significance of BMI status here. Please elaborate on it in the context. Authors' response: BMI was not significant for hypertension control and the table has been corrected accordingly, page 17. 7. In line 257, the authors argued the "3.67 times". Please explain this number was generated.

Authors' response:
This was a typo in text and has now been corrected to 3.69, the OR has also been included at the end of the sentence. Page 23 -the sentence has been corrected to 'Hypertensive females whose male partners had controlled hypertension, were 3.69 times more likely to have controlled BP compared to hypertensive females whose partners had uncontrolled hypertension, after adjustment for female BMI and diabetes, OR 3.69 (CI 1.23 -11.12) ( Table 5).' 8. In line 260, please clarify how the consistency between the US study (non-significant) and your study results (assume significantly).

Authors' response:
We have added text to clarify the differences between our study and the US study. Page 23-'The difference in association found by McAdams et al. may be due to their longitudinal study design, larger sample size of 4500 pairs and adjustment for more risk factors, such as salt intake. (8) 9. Please double-check for errors including typos, extra marks, and grammar Authors' response: We have revised text in places for clarity and corrected errors.
Reviewer #2: Thank you the editor in chief, for providing this golden opportunity to me to review the interesting manuscript. This paper used very strong multilevel model to assess the prevalence, and control of HTN in Namibian couples. The researcher also identified those factors which had association with the prevalence and control of HTN in couples. There are very interesting finds which can play a great role in alleviating the increasing burden of NCD. However, to assure its contribution for readers, still it needs a great work. For this matter I tried to put my concerns here below headed as minor and major comments. I hope the author will cover all points and make the manuscript sounder.
Looking for the modified document!! Authors' response: Thank you for taking the time to review are manuscript, we are delighted that you found it interesting and believe the findings can play a role in alleviating the increasing burden of NCDs. Thank you for your comments, they have been very helpful in revising and improving the paper.
Minor Comments: • Line 35-41: In abstract, the result section does not include all relevant findings in line with the topic of the study.
Authors' response: Thank you for highlighting this, we have adjusted the abstract, page 2, working with the word limit, to include the significant factors for HTN within the results section. The results section now reads 'Results : The unadjusted odds ratio of 1.57 (CI 1.10 -2.24) for hypertension among individuals (both sexes) whose partner had hypertension compared to those whose partner did not have hypertension, was attenuated to aOR 1.35 (CI 0.91 -2.00) for females (after adjustment for age, BMI, diabetes, residence, individual and partner education) and aOR 1.42 (CI 0.98 -2.07) for males (after adjustment for age and BMI). Females and males were significantly more likely to be in control of their hypertension if their partner also had controlled hypertension, aOR 3.69 (CI 1.23 -11.12) and aOR 3.00 (CI 1.07 -8.36) respectively.' • Line 88-96: Citation has to be put. Authors' response: Thank you for this comment, Table 1 is now cited and all the text in the paragraph refers to data within the table, page 11.
• Line 171: The appropriate heading needs to be given for the first objective which was "The prevalence of hypertension in couples" and you need to compare both groups too with respect to the outcome variable.
Authors' response: Thank you for this comment, this section of text refers to data in Table 1  Authors' response: Thank you for this suggestion, we have included p-values in the table, using Pearson Chi -Square -***P < 0.01, **P < 0.05, *P < 0.1 (in the table footnotes), this tested the association between individual and partner factors and hypertension status for both males and females. We didn't use comparison statistics to compare male and female variability of hypertension level. Actual p-value are now given within the text whenever they are discussed on page 11.
•  Authors' response: Thank you, we have removed 'individuals' and used 'Males and females' to avoid confusion, page 13 -'Both males and females were significantly more likely to have hypertension if their partner was also hypertensive, OR 1.57 (CI 1.10 -2.24), p= 0.01 (bivariable models in Table 2 and 3).' • Line 229: The association was simply marginal, you discusses as if they had association. What??
Authors' response: We have reworded this text to discuss the statistical significance of the association found, first paragraph of page 21. 'In our analyses, partner hypertension was significantly associated with individual hypertension in unadjusted models (OR 1.57 (CI 1.10 -2.24), Table 2 and 3) and the estimate of this association was only slightly attenuated in adjusted models, however it was no longer statistically significant (female aOR 1.35 (CI 0.91 -2.00), in Table 2 and male aOR 1.42 (0.98 -2.07), in Table 3).' • Line 239: In contrast? Two similar issues are compared. Why you mentioned as a contrast?
Authors' response: Thank you, we have removed 'in contrast' and changed the text to avoid confusion, in paragraph 2 page 21.
• Line 241: Regarding residency, rural or urban category was obtained as a factor? Correct it.
Authors' response: Thank you for this comment, residence was used a hypertension risk factor and the female model found urban residence to be significantly associated with increased odds of hypertension, page 21.
Authors' response: Thank you for highlighting this, this was a typo in text and has now been corrected, the OR has also been included at the end of the sentence, page 23.
Major comments: • The author operationalized the "HTN control" in line 118-119. However, how those who were aware but not controlled were identified in NDHS survey? It has to be mentioned in a clear way. Generally, the way how an author categorized either controlled or uncontrolled HTN is not clear. The survey was not facility based and it was a snapshot. So, how confident is the author to measure and report the individuals' HTN control status.
Authors' response: Thank you for this comment. We have clarified that we follow the DHS definition of controlled and uncontrolled in the methods (page 8) and discuss the limitations of this approach and potential for some misclassification in the limitations (page 26). 'Similarly, following DHS operationalisation of hypertension control using average BP measurements and antihypertensive medication self-report (14) , a binary variable was created to categorise each hypertensive individual as having their hypertension 'Controlled' or 'Uncontrolled'. Individuals were asked 'Have you ever been told by a doctor or other health worker that you have high blood pressure or hypertension?' (14) , those that responded 'Yes' were defined as 'Aware' of their hypertension and the 'No' group were defined as 'Unaware' if they had elevated blood pressure. The Uncontrolled category included hypertensive individuals who were either 'Unaware' or those who were 'Aware' but not controlled (i.e., had elevated blood pressure at the time of survey). The 'Controlled' category was defined as individuals who were 'Aware' but did not have elevated blood pressure at the time of survey.' In our results we have focused the text to the results of spousal concordance for hypertension control, to avoid confusion with hypertension awareness. The low rates of hypertension awareness in Namibia are now raised in the discussion section, with reference to the prevalence of hypertension awareness reported in the DHS final report (page 23).
'Yuyun et al. reviewed articles covering the prevalence of cardiovascular diseases (CVD) in SSA from January 1990 to March 2019 and reported that over 60% of hypertensive adults (>18 years old) were unaware of their condition. (31) The low rates of CVD awareness in SSA were attributed to insufficient health care infrastructure and lack of resource allocation towards NCDs. Low rates of awareness are mirrored in the Namibia DHS final report with 49% of hypertensive females and 61% of hypertensive males being unaware that they had elevated blood pressure.(14)' • Even though secondary data was used, the author has to explain the following points in method part deeply: The study setting? The setting characteristics?, which population data set was used in this analysis?, how many of them fulfilled the inclusion criteria, how many of them were removed/dropped? (492 couples for HTN prevalence Vs 121 for HTN control), what study design was applied ?, how the study subjects were recruited? (all stages of sampling need to be explained in detail), what type of weighting was applied? And why?, how the data quality was assured in NDHS?, how missed variable were managed?, why a Multilevel LR model was applied?, how much was the cluster correlation level (within-cluster correlation)?, how you measured?, at what level of intra-cluster correlation the multilevel analysis is recommended?, what individual and community level factors were considered, how you assessed your model fitness? (The steps of model building have to be explained clearly). Generally, the method section is poor in mentioning above issues. Hence, the authors must incorporate these points seriously.